This invention relates generally to a cowper of the type having no combustion shaft therein. More particularly, this invention relates to a cowper having a combustion chamber positioned above the chequerwork of the cowper and topped by a cupola wherein one or more burners are arranged along the cupola wall. This invention also relates to a novel burner and novel arrangement of burners for the cowper.
In the prior art, conventional cowpers have been provided with an adjoining or internal combustion shaft wherein combustion of a combustion gas (usually enriched blast furnace gas from a blast furnace cowper) is completed before the gas reaches the cupola chamber of the cowper. However, one important disadvantage of such a conventional cowper structure is that the space required for the combustion shaft is not available for blast heating. Moreover, other substantial disadvantages of such conventional cowpers which result from the deflection of hot combustion gases in the cupola of the cowper are well known.
In an effort to eliminate these disadvantages, and to increase the efficiency of the cowper, the space usually provided for an internal combustion shaft has instead been filled with chequer-bricks. Suggestions are also known for cowpers which have no combustion shaft and which are heated from above. However, despite the advantages of these known cowpers without combustion shafts, it will be appreciated by those skilled in the art that it has been impossible to use such cowpers as a practical matter because of the substantial technical and engineering problems which have arisen.
For example, in cowpers with no combustion shaft, only a very short distance is generally available for the burners arranged in the cupola chamber to complete combustion of the gases. Therefore, there is always an ever present danger that the prior art burners will provide incomplete or delayed mixing and combustion upon entry of the gases into the chequerwork. This results in a nonuniform distribution of temperature, along with localized overheating of the chequerwork, which in turn, produces heat damage to the chequerwork and a reduction in efficiency of the cowper process.
Other cowper burners are known in the art wherein the burner or burners are arranged at the edge of a cupola and are pointed upwardly in a vertical direction. As a result, a relatively longer distance is available for the flame to develop than in the case of the burner arrangement described above. However, this latter burner arrangement nevertheless has the disadvantage that, as a result of a possible suction or vacuum from the emerging jets of flames, the combustion gases are deflected by the cupola in a direction counter to the flame jet. As a consequence, there is a greater tendency of the flame to impact upon only selected areas of the chequerwork. This results in nonuniform distribution of the gas over the cross section of the chequerwork wherein the heating surface is poorly utilized and heat stresses arise which may lead to damage or destruction of the chequerwork. The prior art burner arrangement wherein the burners point upwardly has the further disadvantage that the cupola masonry is exposed to disproportionately high thermal stresses.
It is also well known in the prior art for burner arrangements in cowpers of the type having no combustion shafts wherein a plurality of burners are arranged outside the cowper cupola and are connected to the cowper cupola by combustion ducts pointing slightly (tangentially) upwardly. These prior art burner arrangements are such that complete combustion takes place in the combustion duct, and the flue gases entering the cupola are dispersed by the cupola into the chequerwork in a well known conventional manner.
While the above discussed burner arrangements suggest promising solutions to the problems of cowpers without combustion shaft, serious disadvantages have been found during actual use.
For example, while the above-discussed proposed arrangement for the introduction of gases into the cupola chamber does result in better flow thereof along the chequerwork than in the past, this arrangement does not permit uniform distribution of the gas flow over the chequerwork cross-section. It is well known that such uniform distribution is an essential feature for a cowper having no combustion shaft if it is to be successful in practical industrial use. Unfortunately, the above-described cowper structure does not achieve optimum control of the gas flow in the cowper cupola because the inlet speeds of the flue gases are necessarily too high. It is also probable that the above-discussed proposed cowper will not provide the high temperatures and pressures necessary for efficient operation of modern cowpers.
It is believed that the reason that cowpers having no combustion shaft, particularly cowpers for blast furnace heating, have not yet found partical acceptance in industry may be attributed to the disadvantages and difficulties discussed above.